This issue has been resolved in a hot fix for RSA ClearTrust Agent 3.5 for Access Control Module (ACM). Contact RSA Security Customer Support and request hot fix 3.5.0.32. This hot fix addresses this issue by modifying the Agent such that it responds with HTTP 401 status code to the browser if ACM is functioning as a reverse proxy, and responds HTTP 407 status code to the browser functioning as a forward proxy.